The present invention relates to absorbent structures, such as those employed in infant diapers, childcare training pants, adult incontinence products, feminine hygiene products, and the like. More particularly, the present invention relates to absorbent articles having improved combinations of high absorbency and high strength with increased stability.
Absorbent structures composed of superabsorbent particles and cellulosic wood pulp fibers have been employed in conventional absorbent products. Absorbent structures which include multiple layers have also been employed in conventional absorbent products.
In conventional absorbent articles, however, the absorbent structures undergo significant mechanical stress during ordinary use. The absorbent structure can break into multiple segments, or parts of the absorbent structure can shift and move to undesired locations. The in-use dynamics and stresses can frequently cause the absorbent structures to crack, break, rope and slump. When thin absorbent structures are employed, the tendency to slump, crack, break, and/or rope can increase. As a result of the mechanical degradation of the absorbent structure, the absorption characteristics of the absorbent structure degrade. The transport of liquids through the absorbent structure can be impeded, and the leakage of waste materials from the absorbent structure can become excessive. For example, breakage can typically occur along the fold lines imparted for packaging the absorbent products. Where an absorbent structure breaks along a crotch fold line, the rear portion of the absorbent product can become isolated and become substantially unavailable for the absorption of liquids. When the front portion of the product becomes saturated, the product can prematurely leak without utilizing its entire absorbent capacity.
To improve the mechanical integrity of conventional absorbent structures, adhesives have been mixed or otherwise applied to the absorbent fibers. For example, absorbent structures have been stabilized by applying a hot melt adhesive powder agent. Other absorbent structures have been modified by adding a binder material. Still other conventional configurations have employed layers of tissue to wrap the absorbent structure. Further configurations have employed a wet-strength tissue located in a middle region of the thickness of the absorbent structure.
Conventional absorbent structures or cores have been produced by employing various air laying processes, and the airlaid webs have typically been manufactured within a forming chamber. Binder materials or binder fibers have been introduced into the forming chamber for introduction onto the airlaid absorbent structure.
Conventional absorbent structures, such as those described above, have required excessive amounts of adhesive or other binder material to generate desired levels of integrity and wet-strength. In addition, the conventional absorbent structures have not exhibited the desired combinations of softness, low cost, high absorbency rate, low stiffness, and high strength and stability. As a result, there has been a continued need for absorbent structures having improved combinations of wet-integrity and high absorbency.
The present invention provides an absorbent article comprising a backsheet layer, a liquid permeable topsheet layer, and an absorbent body sandwiched between the backsheet layer and topsheet layer. The absorbent body includes a first fibrous stratum having a first quantity of absorbent fibers, a second fibrous stratum having a second quantity of absorbent fibers, and at least a third fibrous stratum which is located between and integrally formed with the first and second fibrous strata. The third fibrous stratum includes a third quantity of absorbent fibers. In particular aspects, the third fibrous stratum includes an operative quantity of a substantially hydrophilic, wet-strength agent which is distributed in the third quantity of absorbent fibers. In other aspects, the wet-strength agent can render the third fibrous stratum substantially non-dispersible.
In it""s various aspects and configurations, the present invention can provide an absorbent structure having an improved combination of softness, low cost and rapid uptake of absorbed liquids. In desired aspects, the invention can provide an improved distribution of absorbed liquid between the various strata of the absorbent structure. In addition, the invention can provide a stabilized absorbent structure which has increased resistance to cracking, breaking, bunching, roping and/or twisting. In desired configurations, the stabilized absorbent structure can exhibit less surface staining, can provide improved distributions of liquid along the length and width of the absorbent structure, and can provide reduced leakage.